Most drugs, even prescription ones, are difficult to overdose on successfully. Zoloft is useless for these purposes (overdosing can cause serotonin syndrome, which can be fatal but is extremely unpleasant and likely to land you in the hospital instead). Ativan can be very useful for ctb attempts since it is a sedative, but it is extremely unlikely to be fatal on its own. Usually benzos are better used to help with anxiety and let you pass out faster during other methods like SN or CO.